1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Related Art
In the field of image forming apparatuses, it has been known in the art that the surface velocity fluctuation of an image carrier causes degradation in image quality, such as irregular pitch and color misalignment. On the other hand, in the field of product printers, the diameter of an image carrier has been increased in order to achieve higher durability, but a larger diameter leads to a larger influence of surface velocity fluctuation.
To achieve both high image quality and high durability, an image carrier is controlled in such a manner that a fluctuation component at a specific frequency caused by a drive mechanism for driving the image carrier is corrected within a narrow range by using a coefficient that has the characteristic of attenuating the fluctuation component.
However, image forming apparatuses include a rotary member such as a lubricant brush that is in contact with an image carrier and is driven at a different surface velocity. The rotation of the rotary member causes a surface velocity fluctuation of the image carrier, which results in degraded image quality.
Some of the known techniques to address the problem include controlling the surface velocity of a rotary member that has an influence on an image carrier (see JP 2004-004573A), bringing a damper roll, which is used for reducing the fluctuation, into contact with an image carrier when the surface velocity of the image carrier fluctuates (see JP 2004-287083A), and the like. Further, an image forming apparatus has been disclosed in which, when there is a large difference in surface velocity between an image carrier and a rotary member in contact with the image carrier, a slip at the contact portion reduces the surface velocity fluctuation to a level such that no further measures are required in order to reduce the surface velocity fluctuation (see JP 2013-025270A).
However, in recent years, there has been a need to arbitrarily change the surface velocity of a rotary member in contact with an image carrier regardless of the surface velocity of the image carrier in order to achieve higher image quality and higher durability. In this regard, the image forming apparatus of JP 2004-004573A cannot reduce the surface velocity fluctuation because the surface velocity of the rotary member cannot be arbitrarily changed. The driver of the image carrier of JP 2004-287083A requires an additional component, and the problems of higher cost and lower reliability arise due to the complicated structure.
A problem with the image forming apparatus of JP 2013-025270A is that even when there is a large difference in surface velocity between the image carrier and the rotary member in contact with the image carrier, the surface velocity fluctuation of the image carrier is not always reduced depending on the surface velocity of the rotary member. For example, there is a case in which the velocity of a photoreceptor drum is affected by the fluctuation of a brush of a supplementary cleaning member despite a velocity difference of at least 30% or more between the brush and the photoreceptor drum.